Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
Science. 2010 Jun 4;328(5983):1246-8. doi: 10.1126/science.1188200.
The nature of quantum spin liquids, a novel state of matter where strong quantum fluctuations destroy the long-range magnetic order even at zero temperature, is a long-standing issue in physics. We measured the low-temperature thermal conductivity of the recently discovered quantum spin liquid candidate, the organic insulator EtMe3Sb[Pd(dmit)2]2. A sizable linear temperature dependence term is clearly resolved in the zero-temperature limit, indicating the presence of gapless excitations with an extremely long mean free path, analogous to excitations near the Fermi surface in pure metals. Its magnetic field dependence suggests a concomitant appearance of spin-gap-like excitations at low temperatures. These findings expose a highly unusual dichotomy that characterizes the low-energy physics of this quantum system.
量子自旋液体的本质是一种新型物质状态，即使在零温度下，强量子涨落也会破坏长程磁序，这是物理学中长期存在的问题。我们测量了最近发现的量子自旋液体候选物——有机绝缘体 EtMe3Sb[Pd(dmit)2]2 的低温热导率。在零温极限下，明显分辨出一个相当大的线性温度依赖项，表明存在具有极长平均自由程的无能隙激发，类似于纯金属中费米面附近的激发。其磁场依赖性表明在低温下同时出现类似自旋能隙的激发。这些发现揭示了这个量子系统的低能物理特性的一种非常不寻常的二分法。
